The present invention relates to a method of producing a mold core and a device therefor. More particularly, the invention is concerned with a method of and a device for producing a mold core formed of green sand and having a steep configuration including thin and thick body sections.
Molding methods such as shell mold method, cold box method and CO.sub.2 methods are conventionally used in the production of mold cores, mainly for the reasons of strength and dimensional precision of the core to be produced. However, mold cores produced by these known methods are generally expensive and causes a difficulty in the regeneration and reuse of molding sands because the core sand has different characteristics from those of green sand used as the material of the master mold.
Under these circumstances, methods have been developed for producing mold cores from the same green sand as that used in the master mold, and these methods have been successfully used in the production of mold cores having comparatively simple configurations. Such methods are disclosed, for example, in Japanese Patent Laid-Open Nos. 139143/1980 and 195555/1982.
One of such methods employs a longitudinally split type die box which can be split into two parts between which is formed a mold cavity which receives green sand under pressure so as to form a mold core. However, if a mold core having a steep configuration is to be formed by such a known method, difficulties are experienced since it is troublesome to compact or dense the molding sand uniformly over the entire surface of the mold core. In order to avoid producing any non-uniformly compacted mold core, it has been proposed to charge an excess amount of molding sand into a core box. However, such a proposal is still unsuccessful in that it cannot ensure the required uniformity of the sand in the mold core and required high degree of dimensional accuracy particularly when the mold core has a steep configuration.